Stockholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended							9 Months Ended		12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Aug. 30, 2016
Equity [Abstract]
Common stock repurchase authorized											$ 5,000,000
Repurchase of common stock, shares	18,127							18,127		0
Common stock repurchase, average price per share	$ 19.75							$ 19.75
Share repurchase program, remaining amount	$ 4,642,000							$ 4,642,000
Dividends declared, per share	$ 0.17	$ 0.17	$ 0.17	$ 0.14	$ 0.14	$ 0.14	$ 0.14	$ 0.51	$ 0.42
Dividends paid, per share	$ 0.17	$ 0.17	$ 0.17	$ 0.14	$ 0.14	$ 0.14	$ 0.14
Dividend payments, amount	$ 1,937,000				$ 1,585,000			$ 5,813,374	$ 4,750,000